With my Xmas money burning a hole in my pocket, I've decided to splash out and finally get myself a Roomba. After looking around though, I'm more confused than ever as to which is going to be the most suitable, so I thought I'd try to avail myself of the expertise on this forum . . .

My budget could just about stretch to the 760 - I can get the most up-to-date CHM, HEPA filters and all of the improvements to the navigation algorithms and collision detection. However, you don't get virtual lighthouse compatibility until you reach 780/790 (far too expensive), thus the Roomba is less efficient at cleaning each room and may find it hard to find its way back to the docking station. I really want to be able to schedule it to run when I'm at work, so lighthouses seem pretty important. Were I to opt instead for the 581, it appears that the CHM is less effective - potentially negating any efficiency gains delivered by the lighthouses.

I'd be interested to hear people's experiences - are the lighthouses a pretty crucial bit of kit, or are they just a nice to have? Are there any tried and tested ways to pimp a 5- or 6-series Roomba to bring them in line with the 7-series functionality?